Glaucoma is a group of eye diseases that share a distinct type of optic nerve damage that can lead to blindness. A major difficulty of this disease is that most people who have glaucoma do not notice any symptoms until they begin to lose substantial segments of their visual function and in particular visual field. This visual loss is permanent and irreversible. Another major difficulty is that, without years of monitoring individual patients, it is impossible for clinicians to distinguish patients with rapidly progressive glaucoma, the high-risk patients, from those with a more benign course. Consequently, there is no way to target high-risk patients for more aggressive therapy. Chronic glaucoma is truly “the silent blinding disease”. The World Health Organization estimates that the number of people worldwide affected by glaucoma is approximately 13.5 million. Currently, about 300,000 Canadians are diagnosed with glaucoma and it is estimated that another 150,000 Canadians have glaucoma but remain undiagnosed.
Preventive detection of the most common type of glaucoma, primary open angle glaucoma, is challenging because until the disease is in an advanced stage, primary open-angle glaucoma is asymptomatic. Furthermore, because the lost field of vision is usually peripheral, i.e. outside of the region of central vision, patients do not notice it at first.
It is known that while a high intraocular pressure (IOP) is related to glaucoma. However, other factors such as disturbances of blood flow in the optic nerve head may interact with intraocular pressure to affect the optic nerve with or without elevated IOP. Furthermore, in many cases of primary open angle glaucoma, the patient's intraocular pressure is statistically normal which is referred to as normal tension glaucoma. In open angle glaucoma, early detection is further complicated by the fact that the intraocular pressure is commonly normal during standard clinical screening. Because optic nerve examination and perimeter testing are not always performed in addition to intraocular pressure measurement in normal screening visits of those patients at risk, normal tension glaucoma and open angle glaucoma are under diagnosed until the disease has resulted in irreversible damage to the vision.
Thus, identifying people with risk factors would permit the effective use of techniques that detect glaucoma in its early stages, and allow earlier treatment, which in some cases stabilize the progression of glaucoma.
There is currently no methodology to predict which patients' eyesight will deteriorate rapidly from those that will deteriorate slowly. Currently the only apparatus that can estimate the biomechanical properties of the eye in vivo in situ, a confocal scanning laser opthalmoscope, requires that the intraocular pressure be manipulated and that two imaging sessions occur several weeks or months apart. This process is neither rapid nor non-invasive. As of today, no rapid, non-invasive test to quantify the biomechanical properties of the eye in vivo in situ allowing clinicians to identify glaucoma patients at high risk of rapid visual field loss exist. Once identified, such high-risk patients could be treated more aggressively in order to prevent visual field loss.